Epitaxial growth and optical properties of Mg3N2, Zn3N2, and alloys
| dc.contributor.author | Wu, Peng | |
| dc.contributor.supervisor | Tiedje, J. Thomas | |
| dc.date.accessioned | 2019-04-24T23:44:39Z | |
| dc.date.available | 2019-04-24T23:44:39Z | |
| dc.date.copyright | 2019 | en_US |
| dc.date.issued | 2019-04-24 | |
| dc.degree.department | Department of Electrical and Computer Engineering | en_US |
| dc.degree.level | Doctor of Philosophy Ph.D. | en_US |
| dc.description.abstract | Zinc nitride and magnesium nitride are examples of the relatively unexplored II3V2 group of semiconductor materials. These materials have potential applications in the electronics industry due to their excellent optical and electrical properties. This study mainly focuses on the growth and characterization of the new semiconductor materials: zinc nitride, magnesium nitride, and their alloys. The (100) oriented zinc nitride thin films were grown on both (110) sapphire substrates and (100) MgO substrates by plasma-assisted molecular beam epitaxy (MBE). The typical growth rate is in the range of 0.02-0.06 nm/s, the growth temperature is in the range of 140-180 oC, and background nitrogen pressure is around 10-5 Torr. The growth process was monitored by in-situ: reflection high energy electron diffraction (RHEED) and optical reflectivity. The RHEED and X-ray diffraction patterns of the zinc nitride indicate that the film is a single crystal material. The in-situ optical reflectivity pattern of the zinc nitride shows interference oscillations, and these oscillations are damped out as the thickness increases. The reflectivity as a function of time was accurately simulated by an optical equation. The optical constants of the thin films, the growth rate, and the thickness were derived from the simulation of the in-situ reflectance. The X-ray diffraction shows that (400) oriented zinc nitride thin films were grown on both A-plane (110) sapphire substrates and (100) MgO substrates. Optical transmittance measurements were performed on the zinc nitride thin films. The spectrum of the zinc nitride transmittance indicates that zinc nitride has a high optical absorption in the visible light region. The absorption coefficient was calculated from the transmittance spectrum, and the optical band gap of the zinc nitride thin film was found to be 1.25-1.28 eV. Ellipsometry measurements suggested that the refractive index of zinc nitride is 2.3-2.7, and the extinction coefficient is ~0.5-0.7 in the energy range 1.5-3.0 eV. The electron transport measurement shows that the single crystal zinc nitride has a mobility as high as 395 cm2 /Vs. A plasma-assisted MBE system was employed for magnesium nitride growth. The growth temperature was in the range of 300-350 oC. RHEED and laser reflectivity were employed during growth. The RHEED and X-ray diffraction patterns indicated that the epilayers are single crystal films. The optical laser reflectivity was well fitted by a modified optical equation. The optical constants and growth rate were derived from the simulation. X-ray diffraction showed that (400) oriented single crystal magnesium nitride films were grown on (100) MgO substrates. The optical transmittance spectra show that the magnesium nitride has a high absorption below 500 nm. The calculated absorption coefficient is as high as 4x10-4 cm-1 in the range of ~2.5-3.0 eV. The optical band gap was estimated to be ~2.5 eV. Ellipsometry measurements showed that the refractive index of the magnesium nitride is 2.3-2.75 and the extinction coefficient is less than 0.3 in the energy range of 1.5-3.0 eV. Zinc nitride-magnesium nitride (Zn3-3xMg3xN2) alloys were grown on (100) YSZ substrates by sputtering. The bandgap ranged from 1.2 eV to 2.1 eV for Mg content x in the 0-0.59 range. One film with a bandgap of ~1.4 eV and Mg content of 0.18 has the relatively high mobility of 47 cm2 /Vs which was expected for photovoltaics application. | en_US |
| dc.description.scholarlevel | Graduate | en_US |
| dc.identifier.bibliographicCitation | Molecular beam epitaxy growth and optical properties of single crystal Zn3N2 films, Peng Wu, Tom Tiedje, Semiconductor Science and Technology 31(10):10LT01(2016) DOI: 10.1088/0268-1242/31/10/10LT01 | en_US |
| dc.identifier.bibliographicCitation | Molecular beam epitaxy growth and optical properties of Mg3N2 films, Peng Wu, Tom Tiedje, Applied Physics Letters 113(8) (2018) DOI: 10.1063/1.5035560 | en_US |
| dc.identifier.bibliographicCitation | Bandgap tunable Zn3-3Mg3N2 alloy for earth-abundant solar absorber, Peng Wu, Tom Tiedje, Materials Letters 236 (2019), DOI: 10.1016/j.matlet.2018.11.024 | en_US |
| dc.identifier.uri | http://hdl.handle.net/1828/10755 | |
| dc.language | English | eng |
| dc.language.iso | en | en_US |
| dc.rights | Available to the World Wide Web | en_US |
| dc.subject | Molecular beam epitaxy | en_US |
| dc.subject | Semiconductor | en_US |
| dc.subject | II-V group | en_US |
| dc.subject | optical properties | en_US |
| dc.subject | Zinc nitride | en_US |
| dc.subject | Mg3N2 | en_US |
| dc.subject | ZnMgN alloys | en_US |
| dc.title | Epitaxial growth and optical properties of Mg3N2, Zn3N2, and alloys | en_US |
| dc.type | Thesis | en_US |